The present invention relates generally to foam-in-place packaging. Foam-in-place packaging has been well known and widely used as a protective packaging method for a number of years. The underlying technology is based upon the reaction between two (usually liquid) chemicals that form a solid polymer while at the same time generating a gaseous by-product. In particular, when isocyanate compounds react with polyols and water, the reaction produces both a urethane polymer ("polyurethane") and carbon dioxide. Under proper conditions, the carbon dioxide generated by the reaction will bubble and disperse through the polymer as it hardens to thus form an expanded polymer foam that can be used as a protective material for packaging fragile objects. The process by which the liquid precursors mix as liquids and then expand as not-yet-hardened foam typically takes about 20-30 seconds, thus making feasible its manipulation and use for packaging purposes.
In a first generation of foam-in-place packaging, objects to be protected were placed into containers (e.g. corrugated boxes), and wrapped or draped with a protective material such as a plastic sheet. Thereafter, the polyol and isocyanate were pumped from separate supplies, mixed, and then injected from a gun-like dispenser into the container. If the amount of injected mixture was appropriate, the resulting foam would essentially fill the interior of the container while surrounding the object to provide a custom package. Such relatively straightforward injection practices are still useful in many applications, and an updated injection device is disclosed, for example, in copending and commonly assigned application Ser. No. 08/361,322 filed Dec. 21, 1994 for "Hand Held Dispenser for Foamable Compositions and Dispensing System."
In a next generation of foam-in-place packaging, devices have been developed which concurrently produce plastic bags and fill them with the foamable mixture of polymer precursors. The bag has a vent to permit the carbon dioxide to escape. A packaging operator can simply drop one or more newly made bags into a container carrying an object to be packaged, and then close the container. The foam in the bag continues to generate and expand until it likewise fills the interior of the container while forming a custom-shaped cushion around the object packaged therein. Such bag making systems provide the advantage of injecting the foam into a bag that is immediately closed, rather than requiring the operator to manually dispense the foam. As is known to those familiar with such foamable chemicals, they tend to be extremely messy and, if not controlled properly, can cause problems which slow or stop the entire packaging process until the unwanted foam residue can be cleaned up. In more serious circumstances, the foam can even cause its handling machinery to break down leading to further additional delays.
Examples of foam-in-place devices are described in a number of patents and copending applications that are commonly assigned with the present invention. These include inter alia, U.S. Pat. Nos. 4,800,708; 4,854,109, 4,938,007; 5,027,583; 5,139,151 and 5,376,219 and pending applications Ser. Nos. 08/121,751, filed Sep. 15, 1993 and 08/514,010 filed Aug. 11, 1995.
The packaging requirements of various users can, however, differ widely. Thus, any particular given foam-in-place system may not be appropriate or economically viable for every potential user. For example, users who repetitively use foam cushions on a large volume basis are probably most appropriately served by one of the more sophisticated devices such as those described in U.S. Pat. Nos. 5,376,219 or 4,800,708. For less frequent users, the smaller and more compact devices such as that illustrated in pending applications Ser. Nos. 08/121,751 and 08/514,010 may be appropriate, and as mentioned above, some users still prefer the simplest technique of using an injection system with a gun type device that dispenses the foam.
Nevertheless, the market has lacked any foam-in-place packaging system for the user who would otherwise like to take advantage of foam-in-place packaging, but has neither the desire nor the facilities to incorporate any one of the previous mentioned foam-in-bag systems. Accordingly, it has been considered desirable to manufacture a bag in which the foam precursors are separately maintained during storage so that in use, the packaging operator can simply take one of the bags, mix the ingredients by hand (i.e. handle the bag's exterior while mixing the precursors inside), and then place the expanding bag of foam into a package for purposes identical to those just described.
Attempts at making such bags have, however, been generally unsuccessful for reasons that are best illustrated by U.S. Pat. No. 3,419,134 to Fitts, and U.S. Pat. No. 4,232,788 to Roth.
Fitts '134 discloses several variations of a foamable package and a method for forming cellular foam in which the foam precursors are always placed in two separate smaller bags, and in one version of which are placed inside a larger bag. According to Fitts, there are rupturable "partitions" or "walls" between the bags, so that when the operator physically breaks the partitions, the chemicals will mix and form foam. The Roth '788 disclosure is essentially the same from a conceptual standpoint. Each of these suffer from some significant disadvantages, however, and essentially neither has appeared on the marketplace in any significant presence.
More recently, however, a more acceptable foam-in-bag cushion precursor has been developed, and the same is described in copending application Ser. No. 08/626,981 filed Apr. 3, 1996 for "Foam-in-Bag Packaging System," which is commonly assigned with the present invention and which is incorporated entirely herein by reference. As set forth therein, an appropriate combination of materials can provide a useful cushion precursor that carries the foamable compositions in separate portions until intentionally mixed by the end user.
The nature of the cushion precursors described in the '981 application are such that they encourage--and favorably so--the end user to manipulate a cushion precursor to thereby break the intended interior seals and thus initiate the foamforming process. This convenience, however, raises additional considerations. One such consideration is the heat generated by the foam-forming reaction, and copending application Ser. No. 08/834,636, filed concurrently herewith for "Thermally Insulated Foam In Bag Cushions," addresses this point, and this application is incorporated entirely herein by reference.
More specifically, the '981 application describes such bags whose interior seals (dividing foam precursors from each other and from the remainder of the bag) are entirely frangible for use in conjunction with mechanical mixing devices. These devices, even though mechanically simple and inexpensive, nevertheless insure that the separate foam-forming components (usually isocyanates and polyols as noted above) are quickly and thoroughly mixed, thus leading to a complete chemical reaction, elimination of undesired unused starting materials, and a high quality foam.
If the '981 cushion precursors are mixed by hand rather than machine, however, the possibility exists that the user will fail to mix the components as thoroughly as would the machine. Ideally, when using the '981-type cushion precursors, the separate foam precursors (often referred to as the "A" and "B" components) are mixed before they have the opportunity to expand into the empty remainder of the bag. When a '981-type bag is hand-mixed, however, the user may break the frangible seals--which offer significant advantages in many circumstances--in an undesired sequence. As a result, separate and unmixed portions of the A and B components can escape into the remainder of the bag, thus raising the possibility that an incomplete reaction will result, with its related disadvantages.
Therefore, there exists the need for a foam-in-place bag system which the end user can keep in shelf storage for an appropriate period of time and which, when it is to be used, can be manually internally ruptured to give a complete mixing of the foam precursors--even in the absence of machine mixing--that eliminates precursor residue and allows proper expansion of the foam in order to form a structurally appropriate packaging cushion.